Coil Pack & firing order

[Barry_D]

Hi Brent,

I haven't posted in a while because work and my MegaSquirt assy has kept me busy. I mounted my Accel coil pack in a convenient place, was going to attach the spark plug wires, and then noticed they hook up two different ways.

The insert that came in the box with the coil pack looks like this:
http://www.BMWupgrades.com/images/coilpack_fo.gif

I realize if it doesn't work one way it's the other, but just wanted to get it right the first time. Anyone feel free to reply.

I'm wiring my MJLJ, MegaSquirt, FI, relays, and fuses today. Mannnnnn....

Barry

[Paratime]

Hey Barry,

You will probably be rather shocked and appalled to find that either order works just as well. Assuming that you have a standard 4 cyl firing order of 1-3-4-2, the only requirement is that opposite cylinders are on the same coil, which end of the coil is which is irrelevant. You can test this if you have an ohm meter and measure the resistance of the various coil towers. The towers labeled 1 and 4 (and 3-2) should have a value, usually in the K ohms, but 1 to 3 or 2 should be infinite, or open circuit.

[Barry_D]

Hey Paratime,

Thanks for posting. My firing order IS 1 3 4 2. After reading your post earlier today I looked closer at my coil pack, and I'm even more confused. The numbers on the coil pack's connectors don't correspond with either picture I posted.

And, I can't get accurate ohm readings. Do me a favor. Tell me how YOUR coil pack is connected in a clockwise manner starting at some point!

Barry

[Paratime]

My coil is labeled the same as the "late" diagram.

4..2
1..3

connector pointing down.

Cylinders 1 and 4 are called pairs, because they are both at TDC at the same time. one will have just finished compression, and the other will have just finished exhaust. both of these cylinders will fire at the same time, because the two plugs are actually at opposite ends of the same coil. it doesn't matter if a spark fires in the exhausting cylinder, because the exhaust has already burnt, and can't burn again. the cylinder on compression will fire, and produce energy. One revolution later, this coil will fire again, except the cylinder that fired last will be in exhaust, and the cylinder that was in exhaust will now be in compression, and will fire.

Sooooo.......

When you put one lead of the ohm meter on the coil terminal labeled 'one', you should get a reading to 'four' but not to 'two' or 'three'(I got 12K but your's will vary, probably 8-20K). And, if you put one lead on 'two', you should get a reading to 'three' but not to 'one' or 'four'.

The 4 cyl coil pack actually contains only two coils. One coil has two ends labeled 1 and 4, while the other has two ends labeled 2 and 3.

Because each coil fires every revolution, you can hook the wires from 1 and 4 to either place on the 1-4 coil, and the same for 2 and 3, can go to either end of the 2-3 coil.

I will be the first to admit, that this is somewhat confusing...

This web page has a picture of how the two plugs are wired.

http://www.autolite.com/products/dis.htm

[Barry_D]

Thanks Paratime,

I think I got it. The final test comes when I attach the battery and crank it. But first, way more wiring to do...

Barry